Drivers are, as usual, cheaper from aliexpress:
New Leadshine AM882 Stepper Drive Stepping Motor Driver 80V 8.2A with Sensorless Detection #SM414 @SD-in Motor Driver from Industry & Business on Aliexpress.com

4 seems a bit excessive to me. You can maybe justify two for the slaved axis, but I doubt you'll see much benefit using them compared to DQ860MA on the other axes.
BOB/Spindle control/ESS/Mach3... well if you must.

The cable you've chosen for the stepper motors is fine and also good for the spindle, or you could instead use 4-core 1mm^2 for the spindle. I'd stick with the 1.5mm^2 for everything as it just makes estimating the length required easier.